The present invention relates generally to automotive vehicle lift systems having a pair of runways for supporting an automotive vehicle during a vehicle inspection or service procedure, and in particular, to a method and apparatus for utilizing a machine vision vehicle wheel alignment system to measure a level condition of the vehicle lift system runways and to provide measurements associated with the runway elevation positions.
During a vehicle wheel alignment service procedure, it is common for a vehicle undergoing the service procedure to be positioned on an automotive vehicle lift system to enable a technician to raise and lower the vehicle, as is required to access various components on the underside of the vehicle. A wide variety of automotive vehicle lift systems are known. One type of automotive vehicle lift system provides a pair of vertically adjustable runways on which the vehicle wheels are disposed. The runways may be either independent of each other, or coupled together with a connecting structure. Examples of vehicle lift systems employing two vertically adjustable runways include the model RX scissor lift rack, the model L421 Four-Post lift rack, and the RM parallelogram lift rack, each manufactured and sold by Hunter Engineering Co. of Bridgeton, Mo.
Typically, each runway in an automotive vehicle lift system is provided with one or more actuating mechanisms, such as a hydraulic cylinder or screw drive, which is controlled from a common location to regulate the vertical elevation of the individual runways. For safety reasons, the control system which regulates the actuating mechanisms is generally configured to maintain each runway in substantially the same horizontal plane during changes in elevation. An exemplary lift control system is shown in U.S. Pat. No. 6,189,432 to Colarelli et al. Additionally, a mechanism is commonly provided to “lock” the runways at one or more predetermined heights during elevation or when the runways are stationary, preventing collapse of the automotive vehicle lift system in the event of a failure in one or more of the actuating mechanisms.
When in use, runways of automotive vehicle lift systems may flex, twist, warp, or vary in elevation due to a number of factors. These factors may include the structural design of the runways and associated support structures, forces applied to the runways during elevation or lowering by the actuating mechanisms, or the weight distribution of a vehicle positioned on the runways. For example, the lateral position of a vehicle wheel on a runway can induce a flex in the runway surface by exerting a moment arm of force between the wheel contact point and the attachment point of the associated support structure for that runway.
For some vehicle service procedures, such as vehicle wheel alignment, the “levelness” of the runways on which the vehicle is disposed can influence measurements of the vehicle wheel alignment and suspension geometry. In particular, vehicle wheel camber and caster measurements may be effected by an un-level condition of a runway on which the vehicle wheel rests.
Accordingly, it would be advantageous to provide a method and apparatus which operates in conjunction with a vehicle wheel alignment system to obtain a measure of the “levelness” of the runways of an automotive vehicle lift system, and which utilizes such obtained measurements during the course of a vehicle wheel alignment procedure, or provides such obtained measurements to an operator to enable correction of a runway condition.
It would be further advantageous to provide a wheel alignment method for utilizing measurements of the automotive vehicle lift system to facilitate one or more measurements of a vehicle or vehicle wheel alignment angles.